Keyboards, along with computer pointing devices such as computer mice or trackballs, have long been employed as human-to-computer interface devices. A typical keyboard typically includes a plurality of sub-systems designed to convert keystrokes into electronic signals. In a typical laptop computer, for example, a typical keyboard module may include a plurality of key caps, a biasing arrangement for supporting the key caps in their rest position and during keystroke travel, some form of electrical contact circuitry, and other structures for stiffening the keyboard module as well as for fastening the keyboard module to the laptop computer framework.
To facilitate discussion, FIG. 1 shows a portion of an example keyboard arrangement 100 including a keyboard module 102 attached to a keyboard base plate 104 of the laptop computer. The keyboard base plate 104 represents the mechanical structure of the laptop to which keyboard module 102 is attached. Keyboard module 102 includes a plurality of key caps, of which key cap 110 is representative. Key cap 110 is held in its elevated, rest position (relative to keyboard base plate 104) by a biasing arrangement that includes scissor linkages 112a and 112b. As can be seen in FIG. 1, one end of each scissor linkage couples with key cap 110, with the other end coupled with a keyboard mechanism plate 114. As such, linkages 112a and 112b also perform the function of keeping key cap 110 from being detached from the rest of keyboard module 102.
When key cap 110 is depressed, respective slots in the key cap and the keyboard mechanism plate allow scissor linkages 112a and 112b to simulate folding and unfolding actions, thereby enabling key cap 110 to move upward and downward in the Z direction without excessive wobbling. As key cap 110 travels downward, key cap 110 collapses a rubber or resilient dome (conventional and not shown). The collapsing action of the dome creates a characteristic tactile feel and/or force profile.
The downward movement of key cap 110 also causes key cap 110 to make contact with an electrical membrane (not shown), thereby completing the electrical connection that generates and sends a unique electrical signal representing the fact that key cap 110 has been depressed. As key cap 110 is released, the action of the aforementioned dome as well as of the scissor linkages pushes key cap 110 upward to its at-rest position. The details of prior art keyboard module 102 are conventional and will not be discussed in details herein for brevity's sake.
Keyboard module 102 is coupled to keyboard base plate 104 by a plurality of fasteners 120. Keyboard base plate 104 stiffens keyboard module 102 by lending its rigidity to keyboard module 102. This stiffening function is particularly important for a backlit keyboard module, which typically has a large percentage of the mechanism plate 114 removed to allow light to reach the key caps.
A certain keystroke travel distance by key cap 110 is required. With the right amount of keystroke travel, the keyboard user is provided with the appropriate tactile experience when the keys are depressed. For example, some keyboard designs call for a key cap travel distance of about 2.5 millimeters (mm). To accommodate this key cap travel distance, the total thickness in the Z direction of keyboard assembly, including keyboard module 102 and keyboard base plate 104, is typically about 6 mm. Factoring in the heads of fasteners 120, it is not unusual to require a vertical dimension of roughly 6.6 mm in the laptop to accommodate a keyboard assembly.
As devices such as laptop computers become smaller, thinner and more sophisticated, there is less room to incorporate a keyboard assembly into the electronic device. Accordingly, there exists a need for an improved keyboard assembly that is thinner, smaller, and/or incorporates innovative features not found in current keyboards. The present patent application is directed toward such an improved keyboard assembly.